1968 400 Coupe, verdoro green, black vinyl top 1968 400 Convertible, verdoro green, black top 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver)
All the ones Ive seen appeared to be mounted with just screws. However many of the screws looked like they had been over tightened and had distorted the mounting holes. Oops!
You have to remember, back when these cars were made, they didn't have the technology to make rigid plastic parts. Metal inserts/bases were common practice. Re-pops use a rigid plastic base.